ACL Tears and ACL Reconstruction

01  The injury

What happens when the ACL tears

The anterior cruciate ligament runs through the center of the knee and keeps the shinbone from sliding forward and rotating beneath the thighbone. It matters most when you plant, cut, pivot, or land. Most ACL tears happen without contact, as the athlete changes direction or lands from a jump. Many describe a pop, the knee swells within hours, and the knee feels like it shifts or gives way when they try to pivot.

The ACL rarely tears alone. The same event often injures the meniscus, the cartilage cushion that protects the joint, along with the joint surface and the other ligaments. The ligaments on the outside back corner of the knee, the posterolateral corner, are easy to miss and matter for the long-term success of a reconstruction. In a study of skeletally immature patients with ACL tears that I coauthored, MRI showed a posterolateral corner injury in 52% of knees, and a complete tear of one of its components in 14%.

That is why I review the MRI myself and examine the whole knee. Treating the ACL and missing what came with it is one of the more common reasons a reconstruction fails.

02  The first decision

Does every torn ACL need surgery?

No. In a randomized trial of young, active adults with an acute ACL tear, structured rehabilitation with the option of later reconstruction produced the same two-year knee scores as rehabilitation with early reconstruction. Some patients in that rehabilitation-first group never needed surgery. Others went on to reconstruction when the knee kept giving way.

For athletes who plan to return to cutting, pivoting, and jumping sports, the picture changes. A knee that keeps giving way keeps damaging itself. In young patients, waiting more than 12 weeks to reconstruct a torn ACL has been associated with more irreparable medial meniscus tears and more cartilage injury at the time of surgery, and the association was stronger when the patient reported episodes of instability.

The factors I weigh are:

• Your sport and how much it demands cutting, pivoting, and landing
• Your age, and for children, how much growth remains
• Whether the knee is giving way in daily activity or sport
• Meniscus and cartilage injuries, especially a repairable meniscus tear
• Injuries to other ligaments
• Where you are in your season and your career

03  Young athletes

ACL tears in children with open growth plates

ACL tears in middle school and early high school athletes are far more common than they were a generation ago. The traditional advice was to brace the knee and wait until the child stopped growing. The problem is that a child who keeps playing on an unstable knee keeps injuring the meniscus and cartilage, and those injuries are much harder to undo than the ligament.

Reconstruction in a growing child is planned around the growth plates near the knee. Depending on how much growth remains, I use techniques that avoid the growth plates entirely, techniques that cross them with small, carefully placed tunnels, or adult-style reconstruction in teenagers who are close to maturity. Deciding which applies starts with an accurate estimate of growth remaining, using a bone age x-ray of the hand, physical maturity staging, and standing alignment films of both legs when indicated.

Growth disturbance after pediatric ACL reconstruction is uncommon but real. I led a systematic review of 100 studies on the subject. A leg-length difference of more than 10 mm was reported in 2.1% of patients, and an angular deformity of 5 degrees or more in 1.3%. The review also found that most studies did not assess growth remaining or follow patients to the end of growth in a consistent way. In my practice, children who have a reconstruction with growth remaining are followed until they finish growing.

04  The reconstruction

How the reconstruction is built

The torn ACL is not sewn back together. It is replaced with a graft that is passed through tunnels in the thighbone and shinbone at the position of the original ligament. Several decisions go into that operation.

The graft

For young athletes I use the patient's own tissue: the patellar tendon, the quadriceps tendon, or the hamstring tendons. Each has trade-offs in strength, harvest-site symptoms, and suitability for growing patients, and I match the graft to the athlete. Donor tissue (allograft) has a role in older or lower-demand patients and in some revisions, but in a large prospective cohort, the odds of graft rupture were 5.2 times higher with allograft than with patellar tendon autograft. Younger age and higher activity level also raised the risk.

Lateral extra-articular tenodesis (LET)

Some knees have more rotational looseness than an ACL graft alone controls. For those patients I add a lateral extra-articular tenodesis, which uses a strip of the iliotibial band on the outside of the knee to help control rotation. In a randomized trial of 618 patients 25 and younger who were at high risk of failure, adding LET to a hamstring reconstruction reduced graft rupture from 11% to 4% at two years, and reduced overall clinical failure from 40% to 25%. I explain who benefits most in the role of the LET in ACL surgery.

The meniscus and everything else

When the meniscus is torn, I repair it whenever the tear and tissue allow, because the meniscus protects the knee from arthritis. Injuries to the collateral ligaments and posterolateral corner are addressed at the same time when they contribute to instability.

05  Recovery

Phase by phase after ACL reconstruction

These ranges describe a typical course after a primary reconstruction. A meniscus repair, a growing patient, or a revision changes the early restrictions and can lengthen the timeline.

1. Day 0

   Surgery

   Most reconstructions are outpatient, and you go home the same day. Unless a meniscus repair calls for protection, you can put weight on the leg as tolerated with crutches for support.

2. Weeks 0–2

   Swelling, extension, quadriceps

   The early priorities are controlling swelling, getting the knee fully straight, and waking up the quadriceps. Full extension is the single most important early milestone.

3. Weeks 2–6

   Walking normally and restoring motion

   You work off the crutches toward a normal gait while bending progresses. Strengthening of the hip, core, and the other leg continues throughout.

4. Months 2–5

   Strength, control, and running

   Strength work intensifies, with an emphasis on quadriceps strength and single-leg control. Running begins between months 3 and 5, once strength and movement quality meet our thresholds.

5. Months 5–9

   Power, agility, and sport-specific work

   Jumping, landing, cutting, and sport-specific drills progress in stages, first in controlled settings and then with more speed and unpredictability.

6. 9 months or later

   Return to sport

   Return is cleared by testing rather than the calendar: quadriceps strength, hop testing, movement quality, and psychological readiness. In a prospective cohort of athletes in pivoting sports, the reinjury rate fell 51% for each month return was delayed up to nine months, and 38% of those who failed return-to-sport criteria were reinjured compared with 6% of those who passed.

06  The second injury

Protecting both knees after you return

The hardest part of ACL care is the risk of a second injury, and it is highest in the youngest athletes. In a cohort of 354 patients who had reconstruction before age 20, 35% sustained another ACL injury: 18% tore the graft and 18% tore the ACL in the other knee. Males under 18 had the highest graft rupture rate, at 28%. Nearly half of the graft ruptures happened within the first year after surgery.

Expectations matter too. Across 69 studies, 81% of patients returned to some sport after reconstruction, 65% returned to their preinjury level, and 55% returned to competitive sport. Strength, confidence, and the demands of the sport all influenced who got back.

Those numbers are why I build reconstruction around the risk factors we can change: adding LET for high-risk knees, using autograft in young athletes, repairing the meniscus, and clearing return by testing. Injury-prevention training should continue after return, for both legs.

07  Revision

When an ACL reconstruction has failed

A failed reconstruction needs a different workup than a first tear. Common reasons include a new injury, tunnel placement that did not reproduce the native ligament, an unaddressed injury to another ligament or the meniscus, a steep slope of the tibial plateau, and excess rotational laxity.

Revision evaluation includes the MRI, a CT scan to measure the old tunnels, standing x-rays to assess alignment and slope, and the original operative report when it is available. Some revisions can be done in one operation. Others need a first stage to bone-graft widened tunnels before the new reconstruction. An LET, a meniscus repair or transplant, or a realignment osteotomy may be part of the plan.

I see patients for second opinions after failed ACL reconstruction. If you live outside the Baton Rouge area, call the office and we can arrange for your imaging to be reviewed before your visit.

08  Common questions

Questions about ACL tears